Fast, Accurate, and Free Online Conversions
Temperature measurement is a fundamental part of our daily lives, influencing everything from the clothes we wear to the way we cook our food and conduct scientific experiments. Our free online Temperature Converter provides a smooth way to switch between various scientific and colloquial scales, including Celsius, Fahrenheit, Kelvin, and more.
Historically, temperature scales were developed based on different physical phenomena. For example, the Celsius scale, developed by Anders Celsius in 1742, was originally defined by the freezing and boiling points of water. Fahrenheit, on the other hand, was based on a brine solution and the body temperature of a healthy human. Today, scientific standards often rely on the Kelvin scale, which begins at absolute zero—the point where all molecular motion ceases.
In a globalized world, the need for temperature conversion is constant. If you are traveling from the United States to Europe, you'll need to know that 70°F is a comfortable room temperature, roughly equivalent to 21°C. In science and engineering, using the wrong scale can lead to catastrophic errors in calculations, especially in thermodynamics where the Kelvin scale is mandatory.
Our tool uses the most accurate mathematical formulas to ensure your results are precise. Here is a breakdown of the standard conversion formulas:
| From / To | Formula |
|---|---|
| Celsius to Fahrenheit | (°C × 9/5) + 32 |
| Fahrenheit to Celsius | (°F − 32) × 5/9 |
| Celsius to Kelvin | °C + 273.15 |
| Kelvin to Celsius | K − 273.15 |
| Fahrenheit to Kelvin | (°F − 32) × 5/9 + 273.15 |
Let's say you want to convert 100 degrees Celsius to Fahrenheit. This is the boiling point of water at sea level.
One of the most frequent errors in temperature conversion is forgetting that the scales have different starting points (offsets). For example, a "change" of 1 degree Celsius is the same as a "change" of 1 Kelvin, but it is not the same as a "change" of 1 degree Fahrenheit. A Celsius degree is 1.8 times larger than a Fahrenheit degree.
Another common pitfall is the use of the degree symbol. Kelvin is an absolute scale and does not use the degree symbol (°). You should write "273 Kelvin" or "273 K," but not "273°K."
The quest to measure heat began in the early 17th century. The first "thermoscopes" were qualitative, showing only if something was getting hotter or colder. Daniel Gabriel Fahrenheit improved this by using mercury in glass and defining a scale that could be reproduced. Shortly after, Anders Celsius proposed his centigrade scale. In the mid-19th century, Lord Kelvin identified the need for an absolute scale based on thermodynamic principles, leading to the creation of the Kelvin scale used in modern physics.
Absolute zero is the theoretical temperature at which all molecular motion stops. It is defined as 0 Kelvin, which is -273.15° Celsius or -459.67° Fahrenheit.
The US is one of the few countries that hasn't officially switched to the metric system (including Celsius). It became deeply embedded in US manufacturing and daily life during the Industrial Revolution, and the cost of switching is considered prohibitively high.
Yes. The scale was originally called Centigrade because it was divided into 100 parts between the freezing and boiling points of water. It was renamed "Celsius" in 1948 to honor its inventor.
The two scales intersect at -40 degrees. So, -40°C is exactly equal to -40°F.
The Rankine scale is an absolute scale like Kelvin, but it uses the degree increments of the Fahrenheit scale. It is primarily used in engineering systems in the United States.